Help in Asterisk peering with legacy pbx via E1 trunking

Hi all

i have connected my asterisk server to my legacypbx(syntel) via E1 using Digium TE220 .
port1 ===> E1 from provider
Port 2 ==> to the syntel E1 card.

now i need the syntel (epabx) extensions to dialout via asterisk and port1 E1.

what dialplan i need to use so that the syntel extensions can dial out after pressing 0 in there analog phone.
dialplan should wait for the person to dial and also it should give a sound after pressing 0 (the same sound when it was given while we use only syntel)

right now i used below dialplan but it is not good in capturing dtmfs and also if press redial in those phones its not getting full digits in the asterisk .
exten => s,1,Answer()
exten => s,n,Read(OUTNUM,Ringneww,14,2,3)
exten => s,n,Dial(${TRUNKOUT}/${OUTNUM})
exten => s,n,Hangup

Ringneww is the audifile which gives ringback tone .

any other method i can use to dialout with above settings and any recomended chan_dahdi.conf settings required.